Flue gas distribution in heating furnaces



MarchZZ, 1960 w. H. BAILEY, JR 2,929,615

FLUE @As DISTRIBUTION IN HEATING FURNACES Filed Oct. l, 1956 v xx 4' 4Z 2 3 "5 l' 40 INVENTOR.

Wil/iam H Dai/eyl Jr'.

MMM

His Attorn ly nited States Patent fie FLUE GAS DISTRIBUTION IN HEATING FURNACES William H. Dailey, Jr., Toledo, Ohio, assignor, by mesne assignments, to Midland-Ross Corporation, Cleveland, Ohio, a corporation of Ohio Application October 1, 1956, Serial No. 613,239

7 Claims. (Cl. 263-40) T'ne present invention relates to metallurgical furnaces for heating ingots, billets, blooms, slabs and the like preparatory to plastic deformation by rolling, forging, etc. and particularly to an improved method and apparatus for controlling combustion gas, or flue-gas, distribution in slab heaters.

In the control of liuc gas distribution it is desirable that the flow of the flue gases through the heating chamber be maintained in such a manner as to prevent melting, generally referred to as washing or burning, of the initially formed scale at the slab edges and end surfaces.

In the present practice of heating slabs it is customary to pass the work through the heating chamber upon elevated skid rail supports. When the furnace is filled with slabs, the row of slabs supported on the skids separates the heating chamber into top and bottom sections. The flue gases from the furnace are discharged into an exhaust or ue duct ordinarily provided at the charge end of the furnace. Generally the due connects to the furnace from below the stock line, and passes flue gas through a recuperator, if desired, and thence to an exhaust stack. In some cases the ue may connect to the furnace above the stock line, but for purposes of illustration the former type of ilue connection is referred to herein.

With a bottom-connected ue, the gases from the bottom heating section discharge directly into the ue while those gases from the top heating section must pass through side Adowncomers and into the ue. The side downcomers and passages have an inherently high re' sistance to ue gas flow, especially at the stock line, which forces the liuc gases in the top heating section tollowv downward around the slabs before the gases have travelled the entire length of the chamber. As the due gases tiow downward into the bottom heating chamberI the exhaust manifold by adjusting the `relative rates of ow of said ue gases.

2,92%,l5 Patented Mar. 22, 1960 restrictors at the charge end, the operating cylinder of one restrictor being shown responsive to a pressure regulating control device;

Fig. 2 is a fragmentary schematic View taken on line 2-2 of Fig. 1, indicating the position of a downcomer flue passage;

Fig. 3 is a view similar to Fig. l with the operating cylinder of the bottom restrictor being shown responsive to the fuel flow to the burners;

Fig. 4 is a schematic representation of a slab heater furnace having a restrictor of preadjusted size;

Fig. 5 shows an alternate, manually adjustable restrictor.

Referring to Fig. l, the numeral 10 designates the heating chamber of the furnace and the numeral 16 designates the soaking chamber. The furnace is provided with water-cooled pipes or skid rails 11 on which the billets 12 or other work' to be heated are supported within the furnace. The skid rails are supported for part of their length by transverse pipe supports or beams 13. When the furnace is filled with billets 12, the row of billets supported on the skid rails 11 separates the heating chamber into an upper section 14 and lower section 15. l

Heat is supplied to the heating chamber sections 14, 15 and the soaking chamber 16 through burners 17, 1S and 19, respectively, to which fuel and air are supplied. Temperature control means 60, responsive to temperature measuring device 61, any of several well known types, may be employed to adjust the rate of supplying combustion gases, fuel and/or air, to any or all of the burners 17, 18 and 19 through valve 62. (Such temperature measuring and responsive means, for the purpose of simplicity, is only shown in Fig. 3 in cooperation with burner 17.) The products of combustion from burners 17 and 19 travel over the billets towards the charge end an upper bathe or arch 21 is illustrated in Figs. l and 3,

the clearance between the edges of the billets and the furnace wall in the downcomer section may be designed to provide the orifice 20 at the stock line, between the slab edges and the downcomers 22 at the point of miniv mum cross-sectional area, as is illustrated in Fig. 4.

The flue gases from above and below the work being heated discharge into a plenum chamber 52 whose crosssectional area is at least as large as the sum of the effective areas of orifices 20 and 25, thus providing a common i downstream pressure for said orices.

The present invention is primarily concerned with the exhaust flue gas orifices 20 and 2S and the control relating thereto to regulate distribution of combustion gases within the heating chamber section. The remaining construction and operation of the furnace are well known A further advantage is the provisic'mv of a variable `'estricter to regulate the volume of gases owing from one" heating chamber section to correspond with a predeter-v mined volume of gases owing through the other heating chamber section. Y l

For a consideration of what I believe to be novel and my invention, attention is directed to the following specication, the drawing and the concluding claims. A

In the drawings:

Fig. 1 is a schematic representation of Va slab heater furnace embodying' the present invention with gas llow and not illustrated. y

The baille 21, or side Vwing sections or downcomers 22 especially at the minimumcross-sectional area at the stock'line, have an inherent relatively high resistance to the ow of the exhaust gases therethrough, thereby build` ing up a pressure in the upper heating chamber section 14. This pressure tends to force the gases to ilow from the upper section 14 past the billet edges to the lower section 15 of the heating chamber 10 thereby overheating the edges of the billets.

The foregoing is an extensive disclosure of the principles involved in the present invention which will enable persons skilled in the art to take advantage of this invention in similar or equivalent forms.

I claim:

1. In a continuous furnace having a heating chamber through which hot combustion gases flow to an exhaust manifold, and containing elevated work support means which when work is placed thereupon divides said chamber into upper and lower sections, the combination con prising: rst and second burner means for supplying combustion gases to one of said upper and lower sections; third burner means for supplying combustion gases to the other of said upper and lower sections; temperature responsive means for independently controlling the rates of supplying combustion gases from two of said burner means; and control means for controlling the rate of Vsupplying combustion gases from the third of said burner means to maintain a substantially constant pressure difference between said upper and lower sections substantially equal to the static head therebetween.

2. In a continuous heating furnace having a soaking chamber and a heating chamber through which hot combustion gases flow to an exhaust manifold, and containing elevated work support means which when work is placed thereupon divides said heating chamber into upper and lower sections, and separate burner means for each of said upper and lower sections and the soaking chamber, the combination comprising: metering means for measuring the fuel ow through each of said burner means; means for transmitting an impulse representing the sum of the flow through the upper heating section burner means plus the ow through the soaking chamber burner means; means for transmitting an impulse representing the flow through the lower chamber burner means; ratio transmitting means, in operative engagement with the preceding two transmitting means, for transmitting a signal representing the ratio of the sum of the fuel flows through said .upper section burner means and the soaking chamber burner means with the fuel flow through the lower chamber burner means; wall means for regulating the passage of gases from said upper section to the exhaust manifold; an adjustable bafiie for regulating the passage of gases from said lower section to the exhaust manifold; adjusting mechanism for adjusting said adjustable baie; and mechanism operatively associated with said adjusting mechanism for actuating the same in response to the signal from the ratio transmitting means.

3. In a heating furnace, in combination: a heating chamber having elevated work support means and through which hot combustion gases flow, the work when placed upon said support means dividing said chamber into upper and lower sections; a ue for discharging conibustion gases from said chamber; an exhaust chamber discharging into said flue, tirst wall means forming with the work on said support means a rst vertically restricted passage from one of said upper and lower sections into said exhaust chamber; and second wall means, in substantially vertical alignment with said rst restriction, forming with the work on said support a second vertically restricted passage from the other of said upper and lower sections; the horizontal cross-sectional area of said exhaust chamber being greater than the sum of the effective vertical cross-sectional areas of said rst and second restricted passages.

4. The combination according to claim 3 wherein said first wall means comprises an adjustable damper for varying the etective vertical cross-sectional area of the rst restricted passage.

5. In a continuous furnace having a heating chamber through which hot combustion gases ow to an exhaust manifold, and containing elevated work support means which when work is placed thereon divides said chamber into upper and lower sections, the combination comprising: upper burner means for supplying hot combustion gases to said upper section; lower burner means for supplying combustion gases to said lower section; a iirst wall portion forming with work on said support means a iirst restricted ow passage from said upper section to said manifold; a second wall portion forming with work on said support means a restricted flow passage from said lower section to said manifold; and control means comprising temperature responsive 'means operatively connected to adjust the rate of supplying combustion gases from one of said upper and lower burner means, and means for adjusting the rate of supplying combustion gases from the other of said upper and lower burner means to maintain a pressure diierential'between said upper and lower sections substantially constant and equal to the static head pressure therebetween, whereby to substantially prevent passage of gases from one to the other of said sections and thereby avoid overheating the exposed ends of the work being heated.

6. The combination according to claim 5 wherein said means for adjusting the rate of supplying combustion gases from the other of said upper and lower burner means is responsive to the rate of supplying combustion gases to said one of said upper and lower burner means.

7. In a continuous furnace having a heating chamber through which hot combustion gases flow to an exhaust manifold, and containing elevated work support means which when work is placed thereon divides said chamber into upper and lower sections, the combination cornprising: upper burner means for supplying hot combustion gases to said upper section; lower burner means for supplying combustion gases to said 'lower section; a first wall portion forming with work on said support means a iirst restricted flow passage from said upper section to said manifold; a second wall portion forming with work on said support means a second restricted flow passage from said lower section to said manifold; and control means comprising damper means cooperating with one of said iirst and second wall portions, and means responsive to the rates of supplying combustion gases to each of said upper and lower sections and operatively connected to adjust the position of said damper means to maintain a pressure differential between the upper and lower sections substantially constant and equal to the static head pressure therebetweenwhereby to substantially prevent passage of gases from one to the other of said sections and thereby avoid overheating the exposed ends ofthe work being heated.

References Cited in the tile of this patent UNITED STATES PATENTS 1,401,983 Hultgren Jan. 3, 1922 1,861,790 Dreiein June 7, 1932 2,150,613 Stassinet Mar. 14, 1939 2,298,149 Morton Oct. 6, 1942 2,458,624 Morton et al. Jan. 11, 1949 2,628,830 Kerr a Feb. 17, 1953 2,772,084 Pearsall Nov. 27, 1956 

